| Swarm Training C.I.C. | Professional & scientific | 2013 |
| Swdb Financial Ltd | Financial services | 2022 |
| Swea Ltd | Administrative & support | 2016 |
| Sweales Investments Ltd | Real estate | 2025 |
| Sweales Holdings Ltd | Financial services | 2025 |
| Sweat Gymnasium LLP | | 2011 |
| Swedish Biomimetics 3000 Umist Enterprise Limited | Professional & scientific | 2021 |
| Swedish Biomimetics 3000 Umist Technologies Ltd | Professional & scientific | 2018 |
| Sweeney's Removals Limited | Transport & logistics | 2015 |
| Sweep Holdings Ltd | Extraterritorial | 2023 |
| Sweet Briar Office Solutions Ltd | Wholesale & retail | 2012 |
| Sweet Genie Ltd | Wholesale & retail | 2021 |
| Sweet Odyssey Ltd | Wholesale & retail | 2025 |
| Sweet Smiles of Norfolk Limited | Manufacturing | 2021 |
| Sweet the Dessert Shop Limited | Wholesale & retail | 2016 |
| Sweet Treats 4 U Ltd | Wholesale & retail | 2023 |
| Sweet Vanity Ltd | Other services | 2018 |
| Sweetbriar Holidays Limited | Hospitality | 2017 |
| Sweeteez Ltd | Wholesale & retail | 2022 |
| Sweetie Janes Limited | Wholesale & retail | 2025 |
| Sweettastic Churros Ltd | Wholesale & retail | 2021 |
| SWG Sales Limited | Wholesale & retail | 2015 |
| Swift Associates Ltd | Real estate | 2017 |
| Swift Cabs Midlands Ltd | Transport & logistics | 2011 |
| Swift Developments (Norfolk) Limited | Real estate | 2017 |
| Swift Elec & Maintenance Ltd | Construction | 2021 |
| Swift Engineering Solutions Ltd | Manufacturing | 2016 |
| Swift Group Holdings Limited | Financial services | 1994 |
| Swift Host Limited | Real estate | 2022 |
| Swift Imports (Shades) Limited | Wholesale & retail | 1977 |
| Swift Rewinds Ltd | Manufacturing | 2021 |
| Swift Seats Ltd | Wholesale & retail | 2024 |
| Swiftair Ventilation Limited | Manufacturing | 2002 |
| Swiftseal Packaging Limited | Administrative & support | 2024 |
| Swim Wild Swim Free Ltd | Wholesale & retail | 2022 |
| Swinton House Developments Limited | Construction | 2006 |
| Swip SM Limited | Health & social care | 2022 |
| Swished Ltd | Wholesale & retail | 2020 |
| Switch Identity Governance Limited | Information & communication | 2013 |
| SWITCH2EV Limited | Wholesale & retail | 2025 |
| Switched on Group Limited | Wholesale & retail | 2018 |
| Sword Edge Consultancy Services Limited | Professional & scientific | 2024 |
| SWP Worldwide Ltd | Wholesale & retail | 2020 |
| Swpf Group Limited | Financial services | 2024 |
| SWS (Norwich) Limited | Manufacturing | 2002 |
| SY Services Limited | Real estate | 2017 |
| Syan Investments Limited | Financial services | 2026 |
| Sycamore Caterers Limited | Hospitality | 2026 |
| SYD Huggins Quality East Limited | Wholesale & retail | 2000 |
| Syderstone Farms Limited | Professional & scientific | 1966 |
| Sydney East Limited | Real estate | 2019 |
| Syer Consultancy and Service Provision Limited | Health & social care | 2025 |
| Syklops... Limited | Wholesale & retail | 2025 |
| Sykon Group Ltd | Wholesale & retail | 2024 |
| Symbiont Ventures Limited | Professional & scientific | 2024 |
| Symbiontech Ltd | Manufacturing | 2023 |
| Symeus Ltd | Information & communication | 2020 |
| Symmetris Broadband Limited | Information & communication | 2012 |
| Symphonee Ltd | Information & communication | 2025 |
| Symphony (Windows, Doors & Conservatories) Limited | Construction | 1998 |
| Symphony Windows Holdings Limited | Manufacturing | 2019 |
| Symphony Windows Limited | Professional & scientific | 1999 |
| Symposium Coffee Limited | Manufacturing | 2020 |
| Symsolve Limited | Professional & scientific | 2006 |
| Synapsegrid Integrations Ltd | Information & communication | 2025 |
| Synaris Health Limited | Other services | 2021 |
| Syncrotech Limited | Construction | 2014 |
| Syndon Exim Limited | Wholesale & retail | 2024 |
| Synechra Ltd | Professional & scientific | 2025 |
| Synergy Agroscience Ltd | Wholesale & retail | 2012 |
| Synergy Multi Academy Trust | Education | 2012 |
| Synergy Property Design Consultants Limited | Construction | 2001 |
| SYNERGY15 Limited | Information & communication | 2015 |
| Synodor Corporation Group Limited | Manufacturing | 1991 |
| Synolo Strength Limited | Other services | 2024 |
| Synoptical Ltd | Administrative & support | 2017 |
| SYNTEGR8 Limited | Administrative & support | 2024 |
| Synthus Limited | Households | 2013 |
| Syper Ltd | Education | 2021 |
| Syrinix Limited | Manufacturing | 2003 |
| Sys.Works Ltd | Information & communication | 2017 |
| System Printed Circuits Limited | Real estate | 1974 |
| System Solutions (East Anglia) Limited | Information & communication | 2014 |
| Systems People Solutions Ltd | Professional & scientific | 2025 |
| Syvela Ltd | Wholesale & retail | 2025 |
| Szelekta (Hungary) Ltd. | Agriculture & fishing | 1997 |
| Szicsek Palinka Ltd | Wholesale & retail | 2016 |
| SZV Ltd | Extraterritorial | 2023 |
| T & C Hunt (Pharmacy) Limited | Wholesale & retail | 2002 |
| T & H Properties (Anglia) Limited | Extraterritorial | 1985 |
| T & I Communications Ltd | Professional & scientific | 2014 |
| T & J Finishing Ltd | Construction | 2020 |
| T & K J Howard Limited | Other services | 1985 |
| T & M Hotels Limited | Hospitality | 2024 |
| T & S G Property Ltd | Real estate | 2019 |
| T & T Directories Limited | Information & communication | 2012 |
| T & T Fabrications Ltd | Manufacturing | 2017 |
| T & T Wholesale Services Limited | Wholesale & retail | 2021 |
| T and L Roofing Contractors Ltd | Construction | 2022 |
| T B L Concrete Limited | Manufacturing | 1992 |